On 07/07/2015 08:18 AM, Haomai Wang wrote:
Hi All, Currently librbd support aio_read/write with specified callback(AioCompletion). It would be nice for simple caller logic, but it also has some problems: 1. Performance bottleneck: Create/Free AioCompletion and librbd internal finisher thread complete "callback" isn't a *very littleweight" job, especially when "callback" need to update some status with lock hold 2. Call logic: Usually like fio rbd engine, caller will maintain some status with io and rbd callback isn't enough to finish all the jobs related to io. For example, caller need to check each queued io stupidly again when rbd callback finished. So maybe we could add new api which support eventfd, so caller could add eventfd to its event loop and batch reap finished io event and update status or do more things. Any feedback is appreciated!
It seems like a good idea to me. I'm not sure how much overhead it avoids, but letting the callers check status from their own threads is much nicer in general. I'd be curious how much overhead the callback + finisher add. If it's significant, it might make sense to add similar eventfd interfaces lower in the stack too. Josh -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
